Helically-formed pipe winding machine

ABSTRACT

A machine for forming helically wound pipes from a strip (15), having interengaging means on its longitudinal edges, in which a series of rollers (2 and 3) is positioned to form an annulus of rollers (2 and 3) arranged to curve the strip (15) to a helical form within the annulus with the edges of the strip (15) overlapping and means (18, 19) to press the interchanging means on the overlapping edges together to form a pipe (5), in which a pair of feed rollers (16, 17) remote from the means to press (18, 19) controls the rate of feed of the strip (15) to maintain the strip (15) between the feed rollers (16, 17) and the means to press (18, 19) in tension. A modification drives all of the rollers of the annulus synchronously.

This application is a continuation of application Ser. No. 572,534 filedJan. 10, 1984, entitled Helically-Formed Pipe Winding Machine,abandoned.

FIELD OF THE INVENTION

This invention relates to an improved helically wound pipe windingmachine and in particular it relates to a machine of the type in which astrip of any specific configuration is helically wound so that the edgesof the strip overlap and lock together to form a pipe.

THE PRIOR ART

With machines of this type it is customary to use a strip which has aflat body section from which extend outwardly projecting ribs runninglongitudinally on the strip and spaced apart one from another to providereinforcement to the body of the strip. In its usual form such a striphas along one edge a projecting locking member which is shaped so thatit can engage in an appropriately shaped socket at the other edge of thestrip when the strip is being helically wound to form a pipe, andvarious shapes of joining members are known which may be reinforced withadded flaps or extensions on at least one of the edges of the strip.

The machine for winding such a strip may take various forms butaccording to one form, a series of rollers are positioned annularlyabout a longitudinal axis on which the tube is being formed and thestrip is forcibly fed into a helical formation by being driven aroundunder guidance of the rollers of the annulus which define the diameterof the finished pipe.

According to another form, the helical curvature of the strip isachieved by using special feed rollers such for instance as where thepart which engages the strip and the overlapping portion has twodiameters so that, when the two overlapping edges of the strip areforced together to provide the interlock, the strip being fed, and thepipe being formed, have differential pressures applied to them so thatthe join is made under such differential pressure.

The differential pressure is also used to give a required curvature tothe strip to form a tube of a selected diameter, and various prior artliterature refers to different methods of using such pressures to form ahelical convolution at the joining rollers of the strip.

While the art of forming pipes from plastic strips is now well advancedand successful, certain problems exist in maintaining accuracy of thefinal tube and ease of formation as considerable pressures are appliedto the strip when forming it into a pipe because of the ribconstruction.

Such mechanisms also require to be able to readily produce pipes ofvarying diameters and in some cases to vary the diameter duringformation to produce tapered configuration but the present inventionrelates patricularly to the production of pipes of selected sizes by asimple mechanism which uses a feed roller or rollers to move the stripinto the mechanism and then guides the strip into a helical convolutionto cause one edge of the strip to engage the lock to the other edge ofthe strip as the pipe is produced.

OBJECTIVES AND SUMMARY OF THE INVENTION

One of the problems which exists with this type of apparatus is to beable not only to vary the diameter of the pipe being formed but toarrange the helical angle to allow correct relationship between thewidth of the strip and the diameter of the pipe and it is an object ofthe present invention to provide certain improvements to the mechanismto achieve this.

It is a further object to allow the diameter of the pipe being formed tobe varied by simple adjustments to the mechanism.

It is a still further object to so arrange the mechanism that therollers which guide the pipe during its helical convolution aresufficiently closely spaced to avoid bulging of the strip between therollers.

It is a further object to move the strip to allow this helical windingto be effected in a better manner.

A further object is to provide an exact balance of the differentialpressure which will form a strip of selected cross section into a helixto join contiguous edges of the strip to form a continuous pipe.

Basically the present machine comprises a roller cage formed by a pairof rings of generally circular form spaced apart and supporting betweenthem annulus rollers to define a circle equal to the required diameterof the pipe to be formed and these rollers are mounted on adjustingmeans which enable the diameter to be selectively varied.

The strip is fed into the area defined by the annulus rollers at anangle equal to the angle of the helix required so that after oneconvolution under guidance of the rollers the locking member on the edgeof the strip meets with the locking member on the other edge of thestrip of the previous convolution to provide a continuous method offeeding in the strip and forming the pipe.

The invention thus relates to a machine for forming helically woundpipes from a strip in which a frame supports a pair of coaxial ringsspaced apart and supporting rods which carry a series of rollerspositioned to form an annulus of rollers to curve the strip fed into theannulus to a helical form with one edge portion of the strip fed intothe annulus overlapping the opposite edge portion of the strip at theend of the first convolution of the strip to cause roller means at thejoining station to press complementary interengaging configurationstogether to form a pipe, the rollers of the annulus being generallyradially movable by the rings to increase or decrease the size of theannulus, a joining roller being positioned at the meeting of the firstconvolution with the strip and acting with a roller or pressure memberto press the end of the convolution into locking engagement with thesaid strip, a pair of feed rollers being positioned remote from thejoining rollers at a controlled distance therefrom to control the rateof feed of the strip to the joining rollers, driving means beingprovided for at least one of the joining rollers and for at least one ofthe feed rollers, the driving means and/or the rollers being arranged tomaintain the strip between the joining rollers and the control rollersin tension.

The tension can be maintained by variation in the size of the rollers orthe rate of revolution thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a somewhat schematic side elevation of a machine according tothe present invention omitting the forward frame to show more clearlythe chain couplings and the differential drive of the strip.

FIG. 2 is a sectional fragmented view of a strip fed into the machineand showing two convolutions of the strip, showing the actualdifferential drive arrangement for the strip and the pipe but omittingdetails of the frame and guide rollers.

FIG. 3 is an end elevation of a portion of the machine on line 3--3 ofFIG. 1, showing only the drive mechanism by means of which the strip isfed into its helical configuration.

FIG. 4 is a side elevation of a modified form of the invention againwith the forward frame removed, the machine in this case having therollers of the annulus driven by means of a belt so as to rotationallydrive the pipe as it is being formed as well as controlling the feed ofthe strip to the joining locality at which the join is made byoverlapping the edge of the strip with the opposite edge of the firstconvolution.

FIG. 5 is a fragmentary view showing how instead of using independentlyadjustable threaded rods for the rollers of the annulus, a captivesprocket can be used at each rod locality with a chain passing aroundthe annulus, the chain engaging opposite sides of adjacent sprockets,adjacent rods having opposite pitch of the thread.

FIG. 6 is a still further variation showing how a rack-and-pinion can beused with sprockets around which a chain can pass either in the mannerof FIG. 1 or a single chain to simultaneously move all of the rods.

FIG. 7 is an end elevation of the machine showing how the strip can beguided by a series of rings on the rollers engaging between selectedribs of the strip as the tube is being formed.

FIG. 8 is a view on line 8--8 of FIG. 4 but showing only the partsimmediately on the section to show how one of the rings can locate thestrip as it is fed into the helix and showing how the join is made byforcing down a pressure roller onto the join.

FIG. 9 is a view similar to FIG. 8 taken on line 9--9 of FIG. 4 butshowing how the roller adjacent the strip feed-in locality is shortenedand the axle bent to clear the strip and the guide for the strip.

FIG. 10 is a view of a machine similar to that shown in FIGS. 4 to 9 butshowing how the rings which carry the threaded rods can be split andhingedly interconnected so that the machine can be positioned to engagea tube already formed, or some other member which is to have a tubewrapped around it.

FIG. 11 is a section on line 11 of FIG. 10.

FIG. 12 is a fragmented view of the joining rollers of the machine shownin FIG. 1 or 10, showing a driving roller on which the strip being fedin rests, and a pressure roller which forces the join between the stripand start of the first convolution together.

FIG. 13 shows a modified form in which a driven roller, which is drivenas in the form described with reference to FIG. 4, acting with apressure roller, presses together the primary join and a ring makes asecondary seal.

FIG. 14 is a view similar to FIG. 13 but showing the strip inverted tohave the ribs on the inside of the pipe and showing how a modifiedroller can press these edges together to make a primary and thesecondary seal.

FIG. 15 is an end view of a segmented caster roller assembly showing thecarrying bar sectioned.

FIG. 16 is a fragmentary side elevation of such a self-aligning roller,and

FIG. 17 is a schematic view showing how the rollers may be driven byflexible cable means.

The drawings show generally a ribbed strip, but a plain strip with edgeinterlocking means can equally be used.

Referring first to FIGS. 1 to 3, 6 and 12.

The machine comprises a pair of circular ring 1, which are spaced apartand which each carry a series of rollers 2 and 3 extending generally inthe direction of the axis 4 of the pipe 5 being formed, and theserollers 2 and 3 are mounted on rods 6 which have longitudinal racks 7 onthem engaged by pinions 8A on bearing means on the rings 1 so that byrotating the shafts 9 and thus the pinions the position of the rollers2,3 radially can be adjusted. The shaft 9 and pinions are arranged intwo pairs around the periphery of the frames 1 and are driven by chains10 and 11 respectively on each side of sprockets 8 on the shafts 9 sothat alternate rollers 2 and 3 can be independently moved, the reasonfor this being to allow some rollers to remain in an outer position whenforming a small pipe but allowing the other rollers to be projected intooperating position, allowing closer spacing between those rollers in useat the time. Each rod 6 can have either the single roller 2 as shown ortwin rollers 3.

By this arrangement the chain 10 moves the one set of rollers 3 radiallywhile the other chain 11 moves the interposed rollers 2 radially. Thedrives for the chains may be interconnected between the two sides of themachine so that a single control can be used to move all of the rollerssimultaneously if it is required to maintain synchronism.

The rings 1--1 are supported on a main frame 12 to be coaxial but can beorientated independently by a mounting as shown in FIG. 10.

It is not necessary to use dual chains as will be seen from otherembodiments described, but by having the sets of rollers 2,3independently adjustable on the rings 1, one pair of rollers can beallowed to remain out of use. Thus the dual rollers 3 can be moved todefine a smaller diameter of pipe and as the diameter of the pipe isincreased and these rollers 3 require to be moved outwardly by theirrack-and-pinion control, the single rollers 2 can be moved into thespaces between the rolles 3 to again give a close spacing of rollersalthough the rollers are defining a considerably larger diameter.

The mechanism which feeds the strip 15 to the annulus formed by therollers 2 and 3 comprises a pair of drive rollers 16 and 17 remote fromwhere the join is being made, and a further pair of feed rollers 18 and19 where the strip is pressed together to form a junction between thestrip 15 and the first convolution 20 of the pipe 5.

The feed rollers 16 and 17 at the first position engage both sides ofthe strip 15 to form driving means for the strip but the joining rollers18 and 19 are so positioned that the roller 18 engages the strip and theconvolutions forming the pipe but the other roller 19 engages the join21 and extends from this position in the direction of the formed pipe sothat the roller 18 supports the pipe 5 being formed but the roller 19presses the join 21 together but extends to drive the first convolution20 to serve as means for rotating the tube 5 as it is formed.

In the form shown the roller 18 is driven by a chain 23 from the roller17.

The drive for the rollers 16 and 17 and the rollers 18 and 19 is derivedfrom a motor 25 rotating a worm wheel assembly 26 in a gearbox 27, whilethe roller 17 is driven from the shaft of the roller 16 through a pairof gear rollers 28 and 29, the gearing and size of the rollers ensuringthe same peripheral speed of the rollers 16 and 17.

The roller 18 is driven from the shaft of the roller 17 by the chain 23,and the diameter of the roller 18 and the chain sprockets 30 and 31,which are fixed on the shafts of the rollers 17 and 18, are so selectedthat the peripheral speed of the joining roller 18 is slightly higherthan the peripheral speed of the feed rollers 16 and 17 so that the partof the strip between the feed rollers 16 and 17 and the joining rollers18 and 19 is under tension.

Guide means 33 for the strip allow the strip to be fed from a roll toengage the drive rollers 16 and 17 with the strip itself in a horizontalposition and by driving this pair of rollers 18 and 19 at a speeddifferential to the second pair of rollers 18 and 19 any required stresscan be produced at the joining area, and this stress assists in formingthe strip to its helical interlocking configuration so that by thepresent invention it is possible to provide the necessary differentialstress at the joining area and also control the curvature of the stripinto a helical form to move circularly around within the annulus ofrollers 2 and 3 which ensure final determination of the diameter of thepipe being formed and give close control.

By orientating one of the mounting rings 1 in relation to one anotherabout the axis of the pipe, as said, the annulus rollers carried bythese rings can be adjusted in orientation to allow angle adjustmentconsistent with diameter adjustment to be effected and to allowadjustment also for strip width. FIG. 2 shows the need to align thestrip 15 with the angle of the helix so that the strip guide 33 is at anangle to the axis of the pipe being formed.

The strip guide 33 pivots about the shaft 34 which carries the roller 18so that as the roller 18 is adjusted simultaneously with the rollers 2the correct feed of the strip 15 into the annulus takes place, the guide33 carrying the rollers 16 and 17 and gearbox 27 and motor 25 and beingsuspended toward its free end by a threaded rod 35 having axialadjustment means 36 engaging a bracket on a main support frame 37 whichalso supports the rings 1.

The rings 1 are adjustable about their axes on the support frame 37 bymeans such as shown in the embodiment shown in FIG. 10.

The roller 19 rotates on an arm 38 carried by the guide 33, the armhaving a loading screw 39 engage it to allow selection of the pressurethe joining roller 19 exerts on the strip as the strip moves forwardunder the drive exerted by the roller 18.

It can be helpful if one or more of the rollers 2 and 3 which comprisethe roller cage are also driven and rotated about their axes and thisform will be described herein with reference to FIG. 4 to 9, as thesecond embodiment.

Beyond the two rings 1 a series of trolleys are provided which can runon tracks and which themselves can be moved axially in relation to thepipe to select their best position. Each of these trolleys can comprisea pair of frames so arranged that the position of carry rollerssupported by the frames can be varied in relation to the axial positionof the pipe being formed so that when the pipe lies on these carryrollers they form a continuation as it were in the same plane as theguide rollers 2 and 3 which are carried by the rings 1.

In FIG. 4 to 9 a pair of rings 45 carry rods 46, in this case, threadedwhich are axially confined but adjustable by nuts 47 and 48 and carryrollers 49 by means of self-aligning bearings 50, the rings 45 beingsupported by a frame 51 but adjustable thereon about the pipe axis bymeans as shown in FIG. 10. The guide 54 engages the shaft of the roller49A at the joining roller locality which in this case is similar to theremaining rollers 49 which form the annulus, the free end of the stripguide 54 being supported by a link 55 joining it to the frame 51, thisallowing adjustment of the roller 49A simultaneously with the remainingrollers 49 while maintaining correct feed of the strip into the annulus.

As shown in FIG. 8 the roller 56 is mounted on an arm 57 pivoted to abracket 58 connected to the rod 41, and the arm has a loading screw 59.

The roller 49B is shortened and its shaft shaped to allow the guide 54to project past it. In this case, instead of driving only a roller atthe joining locality, all rollers 49, 49A and 49B are driven by a belt62 which encircles the rollers of the annulus and passes around adriving pulley 63 and a take-up drum 64, the drum 64 being rotationallymounted on a support 65 slidably carried on guide rods 66 projectingfrom the frame 51 and engaged by an axially confined threaded adjustmentrod 67 which is rotated by a hand wheel 68, whereby the drum 64 can bepositioned to maintain belt tension around the annulus of rollers 49 andthe driving pulley 63.

The pulley 63 is driven from a motor 70 through a gearbox 71 which alsodrives the two feed rollers 72 and 73 which enage the strip 74 andcontrol the rate of feed to the joining rollers, in this case the roller49A and the pressure roller 56.

In this embodiment therefore the pipe is driven by each of the rollers49, 49A and 49B to give an accurate constant drive, this drive beingslightly faster than the feed by the feed rollers 72 and 73 so that thestrip is maintained in tension between the feed rollers 72 and 73 andthe joining rollers 49A and 56.

The hand-operated adjustment 67-68 could be replaced by spring or fluidpressure operated means moving the support 65 to automatically maintainthe driving tension on the belt 62.

A series of rings 77 on the rollers 49 and if required the roller 49A asshown engage the strip 74 between selected ribs as shown particularly inFIG. 13, in which part of a typical strip is shown comprising a wall 78and ribs 79, one edge portion of the strip having a rib 80 shaped toform a longitudinal groove engaged by a complementary locking projection81 on the other edge of the strip, this ring 77A in this case alsoserving to press a locking flap 82 into the space between the grooveforming rib 80 and the rib 78A, the ribs 78 and 78A having expanded ends83 for further strength, and also the expanded end 83 in the rib 78Aserves to secure the lock by having the edge of the locking flap 82engaged behind the expanded end 83 of the rib 78A.

The above described FIG. 13 of course has the ring 77A located at thejoint, but as shown in FIG. 7 the rings 77 can be positioned at any partof the strip 74 so long as they engage between a pair of the ribs 79,when the strip is provided with ribs, the rings however beingprogressively further along the sequentially arranged rollers 49 tocause particularly the first convolution of the strip to follow anaccurate helical path to cause the locking projection 81 to correctlyengage in the groove in the rib 80 at the end of the first convolution.

Instead of using threaded rods axially positioned by nuts 42 and 43 asshown in FIG. 4, a simultaneous adjustment of all rods 41 can beeffected by means similar to FIG. 1 and as detailed in FIG. 6, theembodiment of FIG. 5 can be used in which a sprocket 84 is captivelymounted in a split ring 45A and is threaded to engage the screw threadon the rod 41.

By having alternate rods opposite thread pitch a chain can be passed onopposite sides of alternate sprockets 85 to extend circularly to driveall sprockets 85 simultaneously but in opposite direction to move allrods axially in the same direction because of the opposite pitch ofalternate threads.

The rods of each embodiment may be plain, thus the rods 6 or 46 or 93can pass through apertures in the rings 1, 45 or 87 and the rings canhave clamping means such as cams to lock the rods. Such an embodiment isshown in FIG. 17 to be later described.

As at times it is necessary to encase a first pipe or similar elongatedmember with a helically-formed pipe, the embodiment of FIGS. 10 and 11show how this can be achieved, the embodiment showing the generalassembly of rollers 49 of FIG. 4 and the strip drive of FIG. 1, but therings 87 are each formed in two parts 87A and 87B, connected together bya hinge 88 and having detent means 89 to lock the rings together.

The frame 50 has slotted ends 91 through which bolts 92 pass to lock therings 87 to the frame 90 but allowing adjustment about the pipe axis toslope the rollers to suit the helix of the pipe, depending on the widthof the strip and the diameter of the pipe being formed. In thisembodiment the threaded rods are designated 93, the feed rollers 94 and95 being driven from the motor 96, the chain 97 driving the roller 98 atthe joining locality while the roller 99 is the pressure roller to pressthe strip 100 onto the joining roller 98. The strip guide 101 is againpivoted on the axis of the shaft 102 of the roller 98 carried by the rod93A, while the free end of the strip guide 101 is suspended by a rod 103with adjustment means 104.

The threaded rods 93 and 93A are controlled axially by nuts 105 captiveon the rings 87.

The roller 99 is carried on a bracket 106 projecting from the stripguide 101 and has loading means in the form of a threaded rod 107.

The roller of the annulus are designated 108.

FIG. 14 shows how a joining roller 110 may be used when the strip 111 isinverted to have the ribs 112 inwardly projecting in a pipe, the drivenjoining roller 113 being plain but the joining roller having a mainpressure face 114 and a ring 115 to press the flap 116 into position,the effect being similar to that described with reference to FIG. 13.

As stated earlier herein there is a critical condition which has to bemet which relates firstly to the angle that the strip is fed into thecage and secondly the angle of the rollers that guide the strip to theirproper helical configuration and ensure that the strip finishes with theexact diameter pipe required.

Therefore according to FIGS. 15 and 16 the rollers 2, 3 or 49 cancomprise a series of segmetns 118 which can adjust independently tovariation in peripheral speed at selected localities of the helix, andare self-aligning with the direction of the force which is being exertedby the annulus rollers.

This can also be achieved by having rollers 121 which themselves neednot rotate, extending along the line of the original rollers, but theserollers 121 are mounted to caster so that they can take the direction ofthe force exerted. Thus, instead of having to very carefully align theannulus rollers the contacting members now align themselves according tothe force at the particular locality.

The bar 127 carries the rollers 121 by means of forks 123 havingspindles 124 engaging the bars 122.

In FIG. 17 is shown one end of a roller 130 supported by a self-aligningbearing 131 on a rod 132, showing how the roller could be driven byflexible drive cables 133 engaging the spindles 134 of the rollers. Aseries of such cables could be synchronously driven from a gearbox withthe required drive outlets. This assembly can be applied for instance inthe form of FIG. 4 as it allows the diameter of the annulus to bevaried.

In this illustration the rod 132 is plane and is locked in position by acam 135 on a lever 136 pivoted at 137 to the ring 138 which correspondsto the rings 1, 45 and 87.

Although in the embodiments described, a roller 19, 56 or 99 is shown asthe pressure member to press the strip onto the joining roller 18, 49Aor 98, this can ge replaced by a flat member, this being particularlyapplicable in FIG. 10 where the pipe is formed over another pipe.

I claim:
 1. A machine for forming helically wound pipe from a plasticribbed preformed strip comprising a frame, a series of rollers axiallyextending and rotatably mounted on spaced apart end rings, said ringsbeing mounted in said frame for rotation in opposite directions, saidrollers being positioned to form an annulus of rollers arranged to curvethe strip to a helical form within the annulus with the edges of thestrip overlapping, joining means carried by said rings to press theoverlapping edges together to form a pipe, said joining means comprisinga joining roller on a shaft supported by said rings and a pressuremember positioned at the meeting of the first convolution with the stripto press the end of the convolution into locking engagement with thesaid strip, a strip guide engaging at one end the said shaft of thejoining roller and projecting tangentially to the annulus, a pair offeed rollers remote from the said joining roller mounted on an oppositeend of said strip guide to control the rate of feed of the strip to thejoining rollers, and driving means for the joining roller and for atleast one of the feed rollers to cause the said joining roller to have agreater peripheral speed than the said feed rollers whereby to maintainthe strip between the joining roller and the said feed rollers intension, whereby when rotating said one ring opposite to the other theangle of the said annulus of rollers and the said strip guide arevariable in relation to the axis of the pipe being formed to compensatefor diameter and strip width.
 2. A machine for forming helically woundpipes from a strip comprising a frame, a series of rollers positioned toform an annulus of rollers arranged to curve a strip to a helical formwithin the annulus with the edges of the strip overlapping, a pair ofrings spaced apart on said frame and mounted for rotation in oppositedirections, said rings engaging shafts of the said rollers whereby theangle of the rollers relative to the axis of the said annulus isadjustable by relative rotation of said rings, means to drive therollers of the annulus synchronously, a joining roller forming part ofthe said annulus and a pressure member positioned at the meeting of thefirst convolution with the strip to press the end of the convolutioninto locking engagment with the said strip, a strip guide engaging atone end the shaft of the said joining roller and projecting tangentiallyto the annulus, a pair of feed rollers at an opposite end of the saidstrip guide remote from the said joining roller, driving means betweenthe said annulus rollers and the feed rollers to cause the said joiningroller to have a greater peripheral speed than the said feed rollers tomaintain the strip between the joining roller and the feed rollers intension whereby when rotating said one ring opposite to the other theangle of the said annulus of rollers and the said strip guide arevariable in relation to the axis of the pipe being formed to compensatefor diameter and strip width.
 3. A machine for forming helically woundpipes from a strip comprising a frame, an annulus of rollers, a pair ofcoaxial rings supported by said frame for rotation in oppositedirections about their axes and spaced apart, supporting rods on saidrings axially adjustable on said rings to carry the rollers of the saidannulus to curve the strip fed into the annulus to a helical form withone edge portion of the strip fed into the annulus overlapping theopposite edge portion of the strip at the end of the first convolutionof the strip, opposite rotational adjustment of the said rings allowingthe angle of the helix of the strip being wound to be changed inrelation to the axis of the pipe being wound, a joining roller formingpart of said annulus at a joining station, pressure means at the joiningroller to press com-plementary interengaging configurations together toform a pipe, said pressure means being a roller having its axis parallelto the axis of the said joining roller, means urging the said pressureroller toward the said joining roller, said rollers of the said annulusand said joining roller being generally radially movable by the saidsupporting rings to increase or decrease the size of the annulus, astrip guide engaging at one end the shaft of the said joining roller andprojecting tangentially to the annulus of rollers, a pair of feedrollers on said strip guide remote from the said joining roller adaptedto be driven to control the rate of feed of the strip to the joiningrollers, driving means for the joining roller and for at least one ofthe feed rollers being arranged to cause the peripheral speed of thesaid joining means to be greater than that of the said feed rollers tomaintain the strip between the joining rollers and the control rollersin tension.
 4. A machine according to claim 1 characterised in that thesaid pressure member is a roller mounted to be urged toward said joiningroller and having its axis parallel thereto.
 5. A machine accordng toclaim 3 characterised by endless driving means extending around theperimeter of the said rollers of the said annulus and engaging the saidrollers to synchronously drive the said rollers, and means to drive thesaid driving means to advance the said strip around within the rollersof the said annulus at a rate to maintain tension in the strip betweenthe said joining roller and the said feed rollers.
 6. A machineaccording to claim 5 wherein the said driving means for the rollers ofthe said annulus comprise a belt passing around the perimeter of thesaid rollers of the annulus, said belt passing also around a drivingroller and a drum remote from the said annulus of rollers and spacedfrom each other, and means to adjust the position of said drum totension the said belt.
 7. A machine according to claim 3 in which thesaid rings are split and provided with hinge means between the saidsplit parts of the said rings to allow the said annulus to be opened toengage over a member about which the said pipe is to be formed.
 8. Amachine according to claim 3 in which the said rollers of the annulusare driven by flexible drive cables engaging the one end of shafts ofthe said rollers and adapted to be driven by drive means.
 9. A machineaccording to claim 3 characterised by a series of rings on the saidrollers of the said annulus spaced to engage at least the said firstconvolution and guide it on a helical path.
 10. A machine according toclaim 3 characterised by a ring on one of the said pair of joiningrollers positioned to press a lock on one edge of the strip which isbeing helically wound into a complementary recess of the other edge ofthe said strip.
 11. A machine for forming helically wound pipes from aplastic longitudinally ribbed strip having interconnecting means alongits longitudinal edge portions comprising a frame, a series oflongitudinally extending rollers forming an annulus about a longitudinalaxis, first and second rings supported on said frame spaced apart aboutsaid axis and rotationally adjustable in opposite direction about saidaxis, radially adjustable bearing means on said rings to engage andsupport shafts of said rollers, means to drive one said roller of theannulus to form a driving roller for the said strip, means to press thestrip on to the said driving roller, a strip guide pivoted at one endabout the axis of the said driving roller and extending normallytherefrom, feed rollers supported on the free end of the said drivingroller arranged to engage the said strip, means coupling the saiddriving roller rotationally to the said feed roller and to drive thesaid driving roller and feed rollers to cause the feed roller to have agreater peripheral speed than the said driving roller whereby tomaintain a strip in tension between the said feed rollers and the saidjoining roller.
 12. A machine according to claim 11 characterised bycoupling means to adjust the said bearings radially simultaneously. 13.A machine according to claim 2 characterised in that the said pressuremember is a roller mounted to be urged toward said joining roller andhaving its axis parallel thereto.